VEGETATION CLASSIFICATION AND MAPPING AT GETTYSBURG NATIONAL MILITARY PARK AND EISENHOWER NATIONAL HISTORIC SITE
Technical Report NPS/NER/NRTR--2006/058
Vegetation classification and mapping was conducted at Gettysburg National Military Park and Eisenhower National Historic Site, creating a current digital geospatial vegetation database for the parks. Classification and mapping was completed jointly for these two parks because the parks are geographically contiguous and are managed by the same natural and cultural resource personnel. Fifteen vegetation associations, Chestnut Oak Forest, Dry Oak Mixed Hardwood Forest, Tuliptree Forest, Modified Successional Forest, Conifer Plantation, Virginia Pine Successional Forest, Sycamore Mixed Hardwood Floodplain Forest, Bottomland Mixed Hardwood Forest, Palustrine Shrub Thicket, Successional Old Field, Agricultural Field, Pasture, Orchard, Wet Meadow, and Reed Canary Grass Riverine Grassland, that occur within the parks were identified and described in detail. These vegetation types are strongly influenced by the varied environmental settings of the parks and the mandate to preserve the topographic, landscape, and cultural features as they were in 1863, such that visitors and historians can fully understand and appreciate the Battle of Gettysburg.
One of the most influential environmental factors on the parks vegetation is the Gettysburg Sill, the large diabase intrusion that supports the forested areas of the Gettysburg National Military Park. Dry Oak Mixed Hardwood Forest is the most abundant forest association in the parks. It is the primary vegetation association in the forested diabase sill area, but also occurs in the historic woodlots scattered throughout Gettysburg National Military Park. Chestnut Oak Forest and Tuliptree Forest are two other, less common, forest associations that occur in the diabase sill area. The low areas surrounding drainages and creeks are another environmental setting in which forested areas persist in the parks. Sycamore Mixed Hardwood Floodplain Forest and Bottomland Mixed Hardwood Forest are typical of these topographically low areas.
Successional Forest association encompasses fragmented, disturbed forest
stands that are dominated by early successional, weedy tree species,
invasive plants, and vines. A few areas of Conifer Plantation remain
where coniferous trees were planted, primarily on privately held lands.
Virginia Pine Successional Forest occurs in two locations in Gettysburg
National Military Park in which Virginia pine (Pinus virginiana)
has become established.
A map showing
the locations of vegetation associations in the parks was created following
the USGS/NPS Vegetation Mapping Program protocols (The Nature Conservancy
and Environmental Systems Research Institute 1994a, b, c). These vegetation
associations were also crosswalked to the Terrestrial and Palustrine
Plant Communities of Pennsylvania (Fike 1999) and to the National Vegetation
Classification System in order to provide a regional and global context
for the parks vegetation. A dichotomous field key was developed
for these vegetation associations to assist with field recognition and
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